/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.nio;

/**
 * A buffer of longs.
 *
 * <p>A long buffer can be created in either of the following ways:
 *
 * <ul>
 *   <li>{@link #allocate(int) Allocate} a new long array and create a buffer based on it;
 *   <li>{@link #wrap(long[]) Wrap} an existing long array to create a new buffer;
 *   <li>Use {@link java.nio.ByteBuffer#asLongBuffer() ByteBuffer.asLongBuffer} to create a long
 *       buffer based on a byte buffer.
 * </ul>
 *
 * @since Android 1.0
 */
public abstract class LongBuffer extends Buffer implements Comparable<LongBuffer> {

  /**
   * Creates a long buffer based on a newly allocated long array.
   *
   * @param capacity the capacity of the new buffer.
   * @return the created long buffer.
   * @throws IllegalArgumentException if {@code capacity} is less than zero.
   * @since Android 1.0
   */
  public static LongBuffer allocate(int capacity) {
    if (capacity < 0) {
      throw new IllegalArgumentException();
    }
    return BufferFactory.newLongBuffer(capacity);
  }

  /**
   * Creates a new long buffer by wrapping the given long array.
   *
   * <p>Calling this method has the same effect as {@code wrap(array, 0, array.length)}.
   *
   * @param array the long array which the new buffer will be based on.
   * @return the created long buffer.
   * @since Android 1.0
   */
  public static LongBuffer wrap(long[] array) {
    return wrap(array, 0, array.length);
  }

  /**
   * Creates a new long buffer by wrapping the given long array.
   *
   * <p>The new buffer's position will be {@code start}, limit will be {@code start + len}, capacity
   * will be the length of the array.
   *
   * @param array the long array which the new buffer will be based on.
   * @param start the start index, must not be negative and not greater than {@code array.length}.
   * @param len the length, must not be negative and not greater than {@code array.length - start}.
   * @return the created long buffer.
   * @exception IndexOutOfBoundsException if either {@code start} or {@code len} is invalid.
   * @since Android 1.0
   */
  public static LongBuffer wrap(long[] array, int start, int len) {
    if (array == null) {
      throw new NullPointerException();
    }
    if (start < 0 || len < 0 || len + start > array.length) {
      throw new IndexOutOfBoundsException();
    }

    LongBuffer buf = BufferFactory.newLongBuffer(array);
    buf.position = start;
    buf.limit = start + len;

    return buf;
  }

  /**
   * Constructs a {@code LongBuffer} with given capacity.
   *
   * @param capacity The capacity of the buffer
   */
  LongBuffer(int capacity) {
    super(capacity);
  }

  /**
   * Returns the long array which this buffer is based on, if there is one.
   *
   * @return the long array which this buffer is based on.
   * @exception ReadOnlyBufferException if this buffer is based on an array, but it is read-only.
   * @exception UnsupportedOperationException if this buffer is not based on an array.
   * @since Android 1.0
   */
  public final long[] array() {
    return protectedArray();
  }

  /**
   * Returns the offset of the long array which this buffer is based on, if there is one.
   *
   * <p>The offset is the index of the array and corresponds to the zero position of the buffer.
   *
   * @return the offset of the long array which this buffer is based on.
   * @exception ReadOnlyBufferException if this buffer is based on an array, but it is read-only.
   * @exception UnsupportedOperationException if this buffer is not based on an array.
   * @since Android 1.0
   */
  public final int arrayOffset() {
    return protectedArrayOffset();
  }

  /**
   * Returns a read-only buffer that shares its content with this buffer.
   *
   * <p>The returned buffer is guaranteed to be a new instance, even if this buffer is read-only
   * itself. The new buffer's position, limit, capacity and mark are the same as this buffer's.
   *
   * <p>The new buffer shares its content with this buffer, which means this buffer's change of
   * content will be visible to the new buffer. The two buffer's position, limit and mark are
   * independent.
   *
   * @return a read-only version of this buffer.
   * @since Android 1.0
   */
  public abstract LongBuffer asReadOnlyBuffer();

  /**
   * Compacts this long buffer.
   *
   * <p>The remaining longs will be moved to the head of the buffer, staring from position zero.
   * Then the position is set to {@code remaining()}; the limit is set to capacity; the mark is
   * cleared.
   *
   * @return this buffer.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public abstract LongBuffer compact();

  /**
   * Compare the remaining longs of this buffer to another long buffer's remaining longs.
   *
   * @param otherBuffer another long buffer.
   * @return a negative value if this is less than {@code otherBuffer}; 0 if this equals to {@code
   *     otherBuffer}; a positive value if this is greater than {@code otherBuffer}
   * @exception ClassCastException if {@code otherBuffer} is not a long buffer.
   * @since Android 1.0
   */
  public int compareTo(LongBuffer otherBuffer) {
    int compareRemaining =
        (remaining() < otherBuffer.remaining()) ? remaining() : otherBuffer.remaining();
    int thisPos = position;
    int otherPos = otherBuffer.position;
    // BEGIN android-changed
    long thisLong, otherLong;
    while (compareRemaining > 0) {
      thisLong = get(thisPos);
      otherLong = otherBuffer.get(otherPos);
      if (thisLong != otherLong) {
        return thisLong < otherLong ? -1 : 1;
      }
      thisPos++;
      otherPos++;
      compareRemaining--;
    }
    // END android-changed
    return remaining() - otherBuffer.remaining();
  }

  /**
   * Returns a duplicated buffer that shares its content with this buffer.
   *
   * <p>The duplicated buffer's position, limit, capacity and mark are the same as this buffer. The
   * duplicated buffer's read-only property and byte order are same as this buffer's, too.
   *
   * <p>The new buffer shares its content with this buffer, which means either buffer's change of
   * content will be visible to the other. The two buffer's position, limit and mark are
   * independent.
   *
   * @return a duplicated buffer that shares its content with this buffer.
   * @since Android 1.0
   */
  public abstract LongBuffer duplicate();

  /**
   * Checks whether this long buffer is equal to another object.
   *
   * <p>If {@code other} is not a long buffer then {@code false} is returned. Two long buffers are
   * equal if and only if their remaining longs are exactly the same. Position, limit, capacity and
   * mark are not considered.
   *
   * @param other the object to compare with this long buffer.
   * @return {@code true} if this long buffer is equal to {@code other}, {@code false} otherwise.
   * @since Android 1.0
   */
  public boolean equals(Object other) {
    if (!(other instanceof LongBuffer)) {
      return false;
    }
    LongBuffer otherBuffer = (LongBuffer) other;

    if (remaining() != otherBuffer.remaining()) {
      return false;
    }

    int myPosition = position;
    int otherPosition = otherBuffer.position;
    boolean equalSoFar = true;
    while (equalSoFar && (myPosition < limit)) {
      equalSoFar = get(myPosition++) == otherBuffer.get(otherPosition++);
    }

    return equalSoFar;
  }

  /**
   * Returns the long at the current position and increase the position by 1.
   *
   * @return the long at the current position.
   * @exception BufferUnderflowException if the position is equal or greater than limit.
   * @since Android 1.0
   */
  public abstract long get();

  /**
   * Reads longs from the current position into the specified long array and increases the position
   * by the number of longs read.
   *
   * <p>Calling this method has the same effect as {@code get(dest, 0, dest.length)}.
   *
   * @param dest the destination long array.
   * @return this buffer.
   * @exception BufferUnderflowException if {@code dest.length} is greater than {@code remaining()}.
   * @since Android 1.0
   */
  public LongBuffer get(long[] dest) {
    return get(dest, 0, dest.length);
  }

  /**
   * Reads longs from the current position into the specified long array, starting from the
   * specified offset, and increase the position by the number of longs read.
   *
   * @param dest the target long array.
   * @param off the offset of the long array, must not be negative and not greater than {@code
   *     dest.length}.
   * @param len the number of longs to read, must be no less than zero and not greater than {@code
   *     dest.length - off}.
   * @return this buffer.
   * @exception IndexOutOfBoundsException if either {@code off} or {@code len} is invalid.
   * @exception BufferUnderflowException if {@code len} is greater than {@code remaining()}.
   * @since Android 1.0
   */
  public LongBuffer get(long[] dest, int off, int len) {
    int length = dest.length;
    if (off < 0 || len < 0 || len > length - off) {
      throw new IndexOutOfBoundsException();
    }

    if (len > remaining()) {
      throw new BufferUnderflowException();
    }
    for (int i = off; i < off + len; i++) {
      dest[i] = get();
    }
    return this;
  }

  /**
   * Returns the long at the specified index; the position is not changed.
   *
   * @param index the index, must not be negative and less than limit.
   * @return the long at the specified index.
   * @exception IndexOutOfBoundsException if index is invalid.
   * @since Android 1.0
   */
  public abstract long get(int index);

  /**
   * Indicates whether this buffer is based on a long array and is read/write.
   *
   * @return {@code true} if this buffer is based on a long array and provides read/write access,
   *     {@code false} otherwise.
   * @since Android 1.0
   */
  public final boolean hasArray() {
    return protectedHasArray();
  }

  /**
   * Calculates this buffer's hash code from the remaining chars. The position, limit, capacity and
   * mark don't affect the hash code.
   *
   * @return the hash code calculated from the remaining longs.
   * @since Android 1.0
   */
  public int hashCode() {
    int myPosition = position;
    int hash = 0;
    long l;
    while (myPosition < limit) {
      l = get(myPosition++);
      hash = hash + ((int) l) ^ ((int) (l >> 32));
    }
    return hash;
  }

  /**
   * Indicates whether this buffer is direct. A direct buffer will try its best to take advantage of
   * native memory APIs and it may not stay in the Java heap, so it is not affected by garbage
   * collection.
   *
   * <p>A long buffer is direct if it is based on a byte buffer and the byte buffer is direct.
   *
   * @return {@code true} if this buffer is direct, {@code false} otherwise.
   * @since Android 1.0
   */
  public abstract boolean isDirect();

  /**
   * Returns the byte order used by this buffer when converting longs from/to bytes.
   *
   * <p>If this buffer is not based on a byte buffer, then always return the platform's native byte
   * order.
   *
   * @return the byte order used by this buffer when converting longs from/to bytes.
   * @since Android 1.0
   */
  public abstract ByteOrder order();

  /**
   * Child class implements this method to realize {@code array()}.
   *
   * @return see {@code array()}
   */
  abstract long[] protectedArray();

  /**
   * Child class implements this method to realize {@code arrayOffset()}.
   *
   * @return see {@code arrayOffset()}
   */
  abstract int protectedArrayOffset();

  /**
   * Child class implements this method to realize {@code hasArray()}.
   *
   * @return see {@code hasArray()}
   */
  abstract boolean protectedHasArray();

  /**
   * Writes the given long to the current position and increases the position by 1.
   *
   * @param l the long to write.
   * @return this buffer.
   * @exception BufferOverflowException if position is equal or greater than limit.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public abstract LongBuffer put(long l);

  /**
   * Writes longs from the given long array to the current position and increases the position by
   * the number of longs written.
   *
   * <p>Calling this method has the same effect as {@code put(src, 0, src.length)}.
   *
   * @param src the source long array.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than {@code src.length}.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public final LongBuffer put(long[] src) {
    return put(src, 0, src.length);
  }

  /**
   * Writes longs from the given long array, starting from the specified offset, to the current
   * position and increases the position by the number of longs written.
   *
   * @param src the source long array.
   * @param off the offset of long array, must not be negative and not greater than {@code
   *     src.length}.
   * @param len the number of longs to write, must be no less than zero and not greater than {@code
   *     src.length - off}.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than {@code len}.
   * @exception IndexOutOfBoundsException if either {@code off} or {@code len} is invalid.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public LongBuffer put(long[] src, int off, int len) {
    int length = src.length;
    if (off < 0 || len < 0 || len > length - off) {
      throw new IndexOutOfBoundsException();
    }

    if (len > remaining()) {
      throw new BufferOverflowException();
    }
    for (int i = off; i < off + len; i++) {
      put(src[i]);
    }
    return this;
  }

  /**
   * Writes all the remaining longs of the {@code src} long buffer to this buffer's current
   * position, and increases both buffers' position by the number of longs copied.
   *
   * @param src the source long buffer.
   * @return this buffer.
   * @exception BufferOverflowException if {@code src.remaining()} is greater than this buffer's
   *     {@code remaining()}.
   * @exception IllegalArgumentException if {@code src} is this buffer.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public LongBuffer put(LongBuffer src) {
    if (src == this) {
      throw new IllegalArgumentException();
    }
    if (src.remaining() > remaining()) {
      throw new BufferOverflowException();
    }
    long[] contents = new long[src.remaining()];
    src.get(contents);
    put(contents);
    return this;
  }

  /**
   * Writes a long to the specified index of this buffer; the position is not changed.
   *
   * @param index the index, must not be negative and less than the limit.
   * @param l the long to write.
   * @return this buffer.
   * @exception IndexOutOfBoundsException if index is invalid.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public abstract LongBuffer put(int index, long l);

  /**
   * Returns a sliced buffer that shares its content with this buffer.
   *
   * <p>The sliced buffer's capacity will be this buffer's {@code remaining()}, and its zero
   * position will correspond to this buffer's current position. The new buffer's position will be
   * 0, limit will be its capacity, and its mark is cleared. The new buffer's read-only property and
   * byte order are same as this buffer's.
   *
   * <p>The new buffer shares its content with this buffer, which means either buffer's change of
   * content will be visible to the other. The two buffer's position, limit and mark are
   * independent.
   *
   * @return a sliced buffer that shares its content with this buffer.
   * @since Android 1.0
   */
  public abstract LongBuffer slice();

  /**
   * Returns a string representing the state of this long buffer.
   *
   * @return a string representing the state of this long buffer.
   * @since Android 1.0
   */
  public String toString() {
    StringBuffer buf = new StringBuffer();
    buf.append(getClass().getName());
    buf.append(", status: capacity="); // $NON-NLS-1$
    buf.append(capacity());
    buf.append(" position="); // $NON-NLS-1$
    buf.append(position());
    buf.append(" limit="); // $NON-NLS-1$
    buf.append(limit());
    return buf.toString();
  }
}
